1. Field of the Invention
The present invention relates to a hoisting and lowering driving engagement multi-row chain incorporated into a hoisting and lowering device, which hoists and lowers a hoisting and lowering table in parallel with a set surface for use by production facilities in various kinds of production fields, a transfer facility in a transportation field, a care facility in a medical welfare field, a stage facility in an art field, and the like.
2. Brief Description of the Related Art
In the field of hoisting and lowering devices, there has been a hoisting and lowering device, which hoists and lowers articles to be hoisted and lowered, such as heavy articles, by use of an engagement chain in which a pair of hoisting and lowering engagement type chains is integrally hoisted and lowered while being engaged with each other. This arrangement is also called a chuck chain (see Japanese Laid-Open Patent Publication No. 11-278797, in particular page 1 and FIG. 1).
In the above-mentioned conventional engagement chain, a chain assembling/disassembling operation is facilitated by incorporating a connecting pin to a pin hole of an internal plate by loose fitting, so called gap filling. However, when a high load due to weight of articles to be hoisted and lowered and the like was applied to such an engagement chain, the connecting pin was bent in the clearance generated between the pin hole of the internal plate and the connecting pin. Thus, there was a problem that fatigue failure was liable to occur in the connecting pin. Further, since the connecting pin was bent in the clearance generated between the pin hole of the internal plate and the connecting pin, a high load due to weight of the above-mentioned articles to be hoisted and lowered was concentrated to the respective plates disposed on the outer plate side press-fitted to the connecting pins, for example outer plates and inner plates and the like in the vicinity of the outer plates. As a result there was a problem that the load balance in the chain width direction worsened so that fatigue strength of the chain was reduced.
Further, in the above-mentioned conventional engagement chain, a roller chain has been adopted in which a roller was rotatably fitted onto a bush. Thus, since the roller was loosely fitted onto the bush, there was a problem that the central axis of the roller was off-centered with respect to the central axis of the connecting pin or the bush at the time of engagement with a sprocket so that contact vibrations or contact noises were generated between the roller and the sprocket. Consequently, the engagement state between the pair of engagement chains generated a shift due to such contact vibrations between the roller and the sprocket, and as a result, there was a problem that the vibrations generated due to the shift in such an engagement state were transmitted to articles to be hoisted and lowered.
Further, since in the above-mentioned engagement chain, the roller was molded separately from the bush, an insufficient wall thickness was obtained, and there was a problem that fatigue failure of the roller was likely to occur when a high load was applied between the roller and the sprocket when articles to be hoisted and lowered such as heavy articles were hoisted.
Accordingly, the present invention has been made for solving the prior art problems, that is, the object of the present invention is to provide a hoisting and lowering driving engagement multi-row chain in which bending of a connecting pin is suppressed to avoid fatigue failure, and at the same time the load carrying balance in a chain width direction is improved. Contact vibrations, and contact noises generated between the chain and a hoisting and lowering sprocket are suppressed, and the endurance of a bush is improved.